1. Field of the Invention
The present invention relates to mobile communication technology, especially relates to devices, methods, mobile communication terminals, computer programs and storage mediums for frequency control.
2. Description of the Prior Art
With the development of mobile communication technology, a plurality of access networks, such as GSM access network, TD-SCDMA access network, WCDMA access network and TD-LTE access network coexist in the conventional mobile communication systems.
Various access networks have different advantages exemplified as follows: network coverage of GSM access network is broader so as to provide better voice call service to users; the network speed of TD-SCDMA access network or WCDMA access network is faster so as to provide high-speed data service to users; while LTE access network can provide even higher-speed service with low delay so as to provide high-definition sound in real time and high-speed data service to users.
In order to fully utilize advantages of various access networks, there is a trend to integrate a plurality of network access techniques in a same operator network. Therefore, user can use one mobile communication terminal to access different access networks. Moreover, different services can be provided through different access networks.
In prior arts, in order to reduce costs, there is a mobile communication terminal which only uses one crystal oscillator and can access different access networks at the same time. The patent document, with application No. 200910201610.7, published as CN102045082A, applicant being Spreadtrum Communications (ShangHai) Inc., discloses a dual standby terminal and control method of automatic frequency control loop thereof.
The dual standby terminal disclosed by the above patent document is shown in FIG. 1, and comprises:
Two RF transceivers 10;
Antennas 11 each corresponding to a different RF transceiver 10;
The signals received by RF transceivers 10 are firstly AD (Analog-to-Digital) converted by an ADC 131 in a baseband processor 13. FO (Frequency Offset) estimation module 132 is used to estimate frequency offsets based on the AD converted signals so that each FO estimation result can be obtained.
A FO selection control module 133 determines a final frequency control signal based on two FO estimation results. A DAC module 134 implements a DA (Digital-to-Analog) conversion on the final frequency signal and outputs the DA converted final frequency signal to an Oscillator 12 so as to control the output frequency of Oscillator 12.
In the above dual standby terminal, FO selection control unit 133 may either utilize the average of the two FO estimation results to determine the final frequency control signal, or use the service status of the system or randomly select one FO estimation result to determine the final frequency control signal.
In the above dual standby terminal and the control method of the automatic frequency control loop thereof, the two FO estimation results are averaged or one of the two FO estimation results is selected, the flexibility is low and service performance can not be guaranteed accordingly.